If my 45-minute drive yesterday morning is anything to go by, I think Slate Auto will have quite the hit on its hands. The startup had one of its prototype trucks in town and asked if I wanted to check it out—no jumping on a plane or having to spend yet another night in an interchangeable hotel room, just a drive from southwest DC to Rockville, Maryland. Easy-peasy. The prototype truck had been well-used, with almost 6,000 miles (9,656 km) showing on the small and minimalist but very legible digital display that also shows your speed and, if you engage reverse, the backup camera…